Viewpoints Geographical Limits of the Southeastern Distribution of Aedes aegypti (Diptera, Culicidae) in Argentina Leonardo M. Dı´az-Nieto 1 , Arnaldo Macia ´ 2 , M. Alejandra Perotti 3 , Corina M. Bero ´n 1 * 1 Centro de Estudios de Biodiversidad y Biotecnologı ´a (CEBB-CIB-FIBA-Mar del Plata) – CONICET, Mar del Plata, Argentina, 2 Divisio ´ n Entomologı ´a, Facultad de Ciencias Naturales y Museo de La Plata (UNLP), La Plata, Argentina, 3 School of Biological Sciences, University of Reading, Reading, United Kingdom Background Aedes aegypti (Linnaeus) is a human-biting mosquito and the primary vector of human dengue and yellow fever viruses; it is also considered the principal vector of Chikungunya virus in Asia [1,2]. In particular, dengue and dengue hemor- rhagic fever constitute an important bur- den to humankind in terms of morbidity and mortality. About 3.6 billion people in the tropics, mainly in Asia, the Western Pacific region, the Caribbean, and Central and South America, live under risk of infection with one or more of the four dengue virus serotypes (DEN-1 to DEN-4), and recent reports estimate over 230 million infections, over 2 million cases of the severe form of the disease, and 21,000 deaths [3]. It is believed that A. aegypti originally migrated from West Africa to the North and South America in the 15th century aboard slave ships, after which yellow fever appeared in the New World. Pre- sumably the yellow fever virus was intro- duced by travellers on these ships, espe- cially African slaves. The adaptation of this insect to survive in human environ- ments was crucial for colonization and development in water storage containers in the holds of sailing ships [4]. At present, A. aegypti lives in close proximity to people, in urban areas, breeding in all types of domestic and peridomestic collections of fresh water, including flower vases, water drums, tins, broken coconut shells, old tires, and gutters. A major range of expansion of Aedes mosquitoes into these urban areas is also attributable to the adaptation of the genera Aedes to breed in water-holding automobile tires [5]. A. aegypti is a tropical and subtropical species spanning a geographical distribu- tion from 35uN to 35uS. Its lower thermal threshold corresponds to 10uC isotherms during the winter, and although it has been found up to 45uN, its presence in colder regions is due to its ability to colonize new areas during the warm season [6]. In South America, the historic direction of dispersal of Aedes mosquitoes has been towards higher latitudes and from tropical to sub-tropical areas, in particular in the Southern Cone. We propose that the southeastern movement of A. aegypti might be related to human migrations from rural areas to towns lacking in a proper housing policy and essential services like water, and sewage disposal systems (http://www. migraciones.gov.ar/pdf_varios/estadisticas /Patria_Grande.pdf) [7]. Between the 1950s, 1960s, and most of the 1970s, epidemic dengue was rare in Central and South America because A. aegypti had been eliminated from most of the countries. The eradication program organized by the Pan American Health Organization (PAHO) was discontinued in the early 1970s, and consequently the mosquito was reintroduced in countries from which it had been eradicated [6,8]. In Argentina, the earliest records of A. aegypti go back to the 1900s and are concurrent with the dengue-like epidemic of 1916, which affected the coastal areas of the Uruguay River (31u449S, 60u319W) [9]. However, in 1986 re-infestation took place along the northern border with Paraguay, spreading over wide areas of the country. Nowadays, the current geo- graphical distribution of A. aegypti in Argentina is wider than during its eradi- cation in 1967 [10,11]. Recently it has been demonstrated that the three A. aegypti main haplogroups identified in Argentina represent different colonization events, probably from neighboring countries: Bolivia, Paraguay, and Brazil (Figure 1A and 1B) [7]. Particularly, in Buenos Aires Province, the most densely populated area of the country, the records of high abundances of well-established popula- tions of A. aegypti were taken in La Plata (capital of the province) and in Buenos Aires (capital city of the country), both located on the east coast, and the south- ernmost findings were recorded in Chas- comu ´s, 132 km from Buenos Aires city (35u339S, 58u009W, Figure 1) [10–15]. On the other hand, cases of dengue have increased in the last few years in Argentina. From January to June 2012, 2,043 patients with symptoms were reported, and 194 were confirmed with serotypes DEN-1, DEN-2, or DEN-3 (http://www.msal.gov.ar/dengue/ images/stories/partes_dengue/parte74.pdf). In 2011 PAHO released an epidemiological alert due to the introduction of DEN-4 serotype in the Americas (http://new.paho. org), with Brazil, Paraguay, and Bolivia countries at high risk of dengue infection with 57,267 possible cases and 5 deaths (Brazil); 10,827 suspected cases and 30 deaths (Paraguay); and 3,233 notified cases with 28 deaths (Bolivia) (Figure 1B) (http:// www.msal.gov.ar/dengue/images/stories/ partes_dengue/parte74.pdf). In the United States, the dispersal of Aedes albopictus Skuse offered an opportu- nity to understand the synanthropic be- havior of Aedes mosquitoes. The mosquito was introduced in 1985 in the continental territory through shipments of used tires from Asia that contained eggs [16]. In subsequent years, the pattern of spread of this container-dwelling species followed the main interstate highways [17], quickly reaching and colonizing several new areas Citation: Dı ´az-Nieto LM, Macia ´ A, Perotti MA, Bero ´ n CM (2013) Geographical Limits of the Southeastern Distribution of Aedes aegypti (Diptera, Culicidae) in Argentina. PLoS Negl Trop Dis 7(1): e1963. doi:10.1371/ journal.pntd.0001963 Editor: Scott L. O’Neill, Monash University, Australia Published January 31, 2013 Copyright: ß 2013 Dı ´az-Nieto et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: This investigation was supported by Agencia Nacional de Promocio ´ n Cientı ´ca y Tecnolo ´ gica (ANPCyT PICT-2007-02069) and by the Universidad Nacional de Mar del Plata (grant 15E/329 EXA 382/07). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. * E-mail: cberon@fiba.org.ar PLOS Neglected Tropical Diseases | www.plosntds.org 1 January 2013 | Volume 7 | Issue 1 | e1963